1. Field of the Invention
The present invention relates to a vibration mechanism having a magneto-spring that can be used for a vibration isolator such, for example, as a suspension unit, a cab mount, an engine mount or the like.
2. Description of the Related Art
Various types of damping materials, dampers, and other control methods have been proposed to prevent vibration and noise that occur in machines and structures built from materials with low internal damping properties, which are required for their strength and rigidity.
In particular, with motor vehicles progressively being made to run at faster and faster speeds, damage to the muscular and nervous systems of vehicle occupants due to exposure to vibration is becoming an issue. Symptoms of these types of damage include fatigue, headaches, stiff shoulders, lower back pain, and vision problems. Normally, springs and damping materials, such as metal springs, air springs, rubber, viscoelastic materials, and dampers, are combined to optimize vibration isolating properties. However, this combination often exhibits opposing characteristics, as in the relationship between the dynamic magnification and the loss factor. That is, if the dynamic magnification is reduced to improve the low-frequency characteristics, this results in a hard spring having a small loss factor, which deteriorates the high-frequency characteristics. In contrast, if the loss factor is increased to improve the high-frequency characteristics, this results in a soft spring having a large dynamic magnification, which is analogous to the damping materials and deteriorates the low frequency characteristics. For that reason, many studies are being conducted on controlling vibration using passive vibration isolators including dynamic dampers, or quasi-active or active control systems. There is a demand for the dampers which can cope with a characteristic change of an object for which vibration isolation is intended, or which is not subject to deterioration with age and influenced by the environment such as temperatures, oils, ozone or the like.
From among these studies, a suspension seat that combines a suspension mechanism set at a low spring constant under a relatively hard cushion has been proposed as a seat that would reduce the vibrational energy from a motor vehicle. Conventional suspension seats attempt to find a point of compromise between isolating high-frequency components of vibrational input and reducing the shocks due to the cushion hitting its bottom point (bottoming or bottom end stop), to optimize the suspension's parameters, but with passive control, limitations always exist.
In recent years, accompanying the practical use of permanent magnets that have a high coercive force and high residual magnetic flux density, research is flourishing in area such as mechanical structures and magnetic systems that utilize magnetic levitation, magnetic bearings, MR dampers, etc., which use magnetic force and magnetic fluidity to control vibration. In particular, magnetic dampers in which eddy currents caused by electromagnetic induction and magnetic damping caused by the effects of magnetic flux are utilized are useful as an attenuating means, and the practical use thereof is expanding.
Meanwhile, because magnetic levitation damping technology makes it possible to support physical objects with no actual physical contact, its merits include reduction of problems related to friction and wear, the capability for motion at very high speeds, and low levels of vibration and noise. Moreover, it can be used in special situations (also a special characteristic of magnets), as well as having the advantage of its force being effective in all directions. For those reasons, magnetic levitation vehicles, magnetic bearings, etc. which apply these special characteristics are being developed.
Of the levitation technologies that utilize these types of magnetic forces, the majority utilizes attractive forces. Magnetic circuits that make use of repulsive forces are difficult to utilize in vibration control systems, due to their instability, the fact that the marked non-linear characteristics of the repulsive forces are difficult to control, and their large spring constant.